We manage a cluster of Open Atrium sites for clients using Aegir. To get a sense of how powerful Aegir is for running a hosted service here is an under 3 minute video of Jeff and I applying today's Drupal security patch to all of our sites.
A Little More Background
A few hours ago, a critical Drupal core security vulnerability that allowed cross site scripting in Drupal 6 core OpenID and a possible apache file executable issue with the File API was identified and fixed by Drupal's Security team. Since Open Atrium Beta 2.1 was running on Drupal 6.13 core, our Open Atrium sites were potentially vulnerable to this security release and we needed to patch our sites with Drupal 6.14. The Open Atrium team released Beta 3 less than two hours after the security announcement, and we were good to run the upgrades.